In the past the agricultural ammonia industry has used a relatively small ammonia applicator mounted to the three point hitch of a tractor. The applicator was built to carry a predetermined number of applicator knives depending on the number of rows to be treated on each pass. An ammonia tank was conveniently mounted on the applicator. The ammonia was divided in a confined manifold chamber across orifices which were placed in the hose fittings that feed the knives. This manifold was part of an expansion valve that maintained a predetermined pressure depending on the quantity per acre and the tractor speed. Placed between the ammonia tank's withdrawal valve and the expansion valve was a quick opening shutoff valve which the operator used to shut down the system as he made his turns at the end of the rows.
The applicator tank was filled from a detached nurse tank by the operator. While this prior system was slow due to its small size, it was probably more consistent across the fields than today's large applicator systems. Currently used large tractors mounted with relatively large tool bars, with a nurse tank in tow, have the capability of covering large tracts of land rather rapidly. Accurate ground speed control of these tractors has made it easier to lay down a given amount of ammonia for a given area, and radar ground speed sensors have removed the error of wheel slippage. With electronic controls, we are sure of the overall quantity of ammonia a given field has received, but still no one is quite sure of where it is in the field due to the variables in the art of distribution across the tool bar.
Distribution manifolds in use prior to my invention were predominantly simple devices having a central inlet opening into a disc shaped chamber, with the hose connector outlets installed in pipe threads that open into the chamber about the periphery. In use, there were typically openings that were not required and that were plugged. The larger grains, such as corn and milo, require fewer applicator knives per tool bar width than the smaller grains like wheat and barley. A forty-five foot tool bar would be a thirteen row machine in corn, requiring a manifold with thirteen outlets with equal lengths of applicator hoses, for example, thirteen hoses of twenty-five feet in length. The same tool bar rigged for small grains could have as many as forty-five knives with forty-five hoses, each twenty-five feet in length, and the user would be applying one third the product through three and one half times as many hoses.
The number and length of hoses is important, because the two forces acting on the distribution of ammonia through a manifold and hoses are gravity and thermal energy. A compact manifold having a reasonably high pressure difference across it on level ground could have its distribution noticeably affected from an uneven heat flow into the applicator hoses, because a liquified gas like ammonia prefers to flow away from heat to a colder area. To date, there has been little fruitful work done to solve the variables in distribution.